package org.checkerframework.framework.type;

import com.sun.source.tree.LambdaExpressionTree;
import com.sun.source.tree.Tree;
import com.sun.source.tree.VariableTree;
import com.sun.tools.javac.code.Symbol;
import java.util.List;
import javax.lang.model.element.Element;
import javax.lang.model.element.ElementKind;
import javax.lang.model.element.TypeElement;
import javax.lang.model.element.TypeParameterElement;
import javax.lang.model.element.VariableElement;
import org.checkerframework.checker.nullness.qual.Nullable;
import org.checkerframework.framework.type.AnnotatedTypeMirror.AnnotatedDeclaredType;
import org.checkerframework.framework.type.AnnotatedTypeMirror.AnnotatedTypeVariable;
import org.checkerframework.framework.type.visitor.AnnotatedTypeScanner;
import org.checkerframework.framework.util.element.ClassTypeParamApplier;
import org.checkerframework.framework.util.element.ElementAnnotationUtil.ErrorTypeKindException;
import org.checkerframework.framework.util.element.ElementAnnotationUtil.UnexpectedAnnotationLocationException;
import org.checkerframework.framework.util.element.MethodApplier;
import org.checkerframework.framework.util.element.MethodTypeParamApplier;
import org.checkerframework.framework.util.element.ParamApplier;
import org.checkerframework.framework.util.element.SuperTypeApplier;
import org.checkerframework.framework.util.element.TypeDeclarationApplier;
import org.checkerframework.framework.util.element.TypeVarUseApplier;
import org.checkerframework.framework.util.element.VariableApplier;
import org.checkerframework.javacutil.BugInCF;
import org.checkerframework.javacutil.ElementUtils;
import org.plumelib.util.IPair;

/**
 * Utility methods for adding the annotations that are stored in an Element to the type that
 * represents that element (or a use of that Element).
 *
 * <p>In a way, this class is a hack: the Type representation for the Elements should contain all
 * annotations that we want. However, due to <a
 * href="https://mail.openjdk.org/pipermail/type-annotations-dev/2013-December/001449.html">javac
 * bugs</a> decoding the type annotations from the Element is necessary.
 *
 * <p>Even once these bugs are fixed, this class might be useful: in TypesIntoElements it is easy to
 * add additional annotations to the element and have them stored in the bytecode by the compiler.
 * It would be more work (and might not work in the end) to instead modify the Type directly. The
 * interaction between TypeFromElement and TypesIntoElements allows us to write the defaulted
 * annotations into the Element and have them read later by other parts.
 */
public final class ElementAnnotationApplier {

  /** Do not instantiate. */
  private ElementAnnotationApplier() {
    throw new AssertionError("Class ElementAnnotationApplier cannot be instantiated.");
  }

  /**
   * Add all of the relevant annotations stored in Element to type. This includes both top-level
   * primary annotations and nested annotations. For the most part the TypeAnnotationPosition of the
   * element annotations are used to locate the annotation in the right AnnotatedTypeMirror location
   * though the individual applier classes may have special rules (such as those for upper and lower
   * bounds and intersections).
   *
   * <p>Note: Element annotations come from two sources.
   *
   * <ol>
   *   <li>Annotations found on elements may represent those in source code or bytecode; these are
   *       added to the element by the compiler.
   *   <li>The annotations may also represent those that were inferred or defaulted by the Checker
   *       Framework after a previous call to this method. The Checker Framework will store any
   *       annotations on declarations back into the elements that represent them (see {@link
   *       org.checkerframework.framework.type.TypesIntoElements}). Subsequent, calls to apply will
   *       encounter these annotations on the provided element.
   * </ol>
   *
   * Note: This is not the ONLY place that annotations are explicitly added to types. See {@link
   * org.checkerframework.framework.type.TypeFromTree}.
   *
   * @param type the type to which we wish to apply the element's annotations
   * @param element an element that possibly contains annotations
   * @param typeFactory the typeFactory used to create the given type
   */
  public static void apply(
      AnnotatedTypeMirror type, Element element, AnnotatedTypeFactory typeFactory) {
    try {
      try {
        applyInternal(type, element, typeFactory);
      } catch (UnexpectedAnnotationLocationException e) {
        reportInvalidLocation(element, typeFactory);
      }
      // Also copy annotations from type parameters to their uses.
      new TypeVarAnnotator().visit(type, typeFactory);
    } catch (ErrorTypeKindException e) {
      // Do nothing if an ERROR TypeKind was found.
      // This is triggered by Issue #244.
    }
  }

  /** Issues an "invalid.annotation.location.bytecode warning. */
  private static void reportInvalidLocation(Element element, AnnotatedTypeFactory typeFactory) {
    Element report = element;
    if (element.getEnclosingElement().getKind() == ElementKind.METHOD) {
      report = element.getEnclosingElement();
    }
    // There's a bug in Java 8 compiler that creates bad bytecode such that an
    // annotation on a lambda parameter is applied to a method parameter. (This bug has
    // been fixed in Java 9.) If this happens, then the location could refer to a
    // location, such as a type argument, that doesn't exist. Since Java 8 bytecode
    // might be on the classpath, catch this exception and ignore the type.
    // TODO: Issue an error if this annotation is from Java 9+ bytecode.
    if (!typeFactory.checker.hasOption("ignoreInvalidAnnotationLocations")) {
      typeFactory.checker.reportWarning(
          element, "invalid.annotation.location.bytecode", ElementUtils.getQualifiedName(report));
    }
  }

  /** Same as apply except that annotations aren't copied from type parameter declarations. */
  private static void applyInternal(
      final AnnotatedTypeMirror type, Element element, AnnotatedTypeFactory typeFactory)
      throws UnexpectedAnnotationLocationException {

    if (element == null) {
      throw new BugInCF("ElementAnnotationUtil.apply: element cannot be null");

    } else if (TypeVarUseApplier.accepts(type, element)) {
      TypeVarUseApplier.apply(type, element, typeFactory);

    } else if (VariableApplier.accepts(type, element)) {
      if (!ElementUtils.isLocalVariable(element)) {
        // For local variables we have the source code,
        // so there is no need to look at the Element.
        // This is needed to avoid a bug in the JDK:
        // https://github.com/eisop/checker-framework/issues/14
        VariableApplier.apply(type, element);
      }

    } else if (MethodApplier.accepts(type, element)) {
      MethodApplier.apply(type, element, typeFactory);

    } else if (TypeDeclarationApplier.accepts(type, element)) {
      TypeDeclarationApplier.apply(type, element, typeFactory);

    } else if (ClassTypeParamApplier.accepts(type, element)) {
      ClassTypeParamApplier.apply((AnnotatedTypeVariable) type, element, typeFactory);

    } else if (MethodTypeParamApplier.accepts(type, element)) {
      MethodTypeParamApplier.apply((AnnotatedTypeVariable) type, element, typeFactory);

    } else if (ParamApplier.accepts(type, element)) {
      ParamApplier.apply(type, (VariableElement) element, typeFactory);

    } else if (isCaptureConvertedTypeVar(element)) {
      // Types resulting from capture conversion cannot have explicit annotations

    } else {
      throw new BugInCF(
          "ElementAnnotationUtil.apply: illegal argument: "
              + element
              + " ["
              + element.getKind()
              + "]"
              + " with type "
              + type);
    }
  }

  /**
   * Annotate the list of supertypes using the annotations on the TypeElement representing a class
   * or interface.
   *
   * @param supertypes types representing supertype declarations of TypeElement
   * @param subtypeElement an element representing the declaration of the class which is a subtype
   *     of supertypes
   */
  public static void annotateSupers(
      List<AnnotatedDeclaredType> supertypes, TypeElement subtypeElement) {
    try {
      SuperTypeApplier.annotateSupers(supertypes, subtypeElement);
    } catch (UnexpectedAnnotationLocationException e) {
      reportInvalidLocation(subtypeElement, supertypes.get(0).atypeFactory);
    }
  }

  /**
   * Helper method to get the lambda tree for ParamApplier. Ideally, this method would be located in
   * ElementAnnotationUtil but since AnnotatedTypeFactory.declarationFromElement is protected, it
   * has been placed here.
   *
   * @param varEle the element that may represent a lambda's parameter
   * @return a LambdaExpressionTree if the varEle represents a parameter in a lambda expression,
   *     otherwise null
   */
  public static @Nullable IPair<VariableTree, LambdaExpressionTree> getParamAndLambdaTree(
      VariableElement varEle, AnnotatedTypeFactory typeFactory) {
    VariableTree paramDecl = (VariableTree) typeFactory.declarationFromElement(varEle);

    if (paramDecl != null) {
      Tree parentTree = typeFactory.getPath(paramDecl).getParentPath().getLeaf();
      if (parentTree != null && parentTree instanceof LambdaExpressionTree) {
        return IPair.of(paramDecl, (LambdaExpressionTree) parentTree);
      }
    }

    return null;
  }

  /**
   * Was the type passed in generated by capture conversion.
   *
   * @param element the element which type represents
   * @return true if type was generated via capture conversion false otherwise
   */
  private static boolean isCaptureConvertedTypeVar(Element element) {
    Element enclosure = element.getEnclosingElement();
    return (((Symbol) enclosure).kind == com.sun.tools.javac.code.Kinds.Kind.NIL);
  }

  /**
   * Annotates uses of type variables with annotation written explicitly on the type parameter
   * declaration and/or its upper bound.
   */
  private static class TypeVarAnnotator extends AnnotatedTypeScanner<Void, AnnotatedTypeFactory> {
    @Override
    public Void visitTypeVariable(AnnotatedTypeVariable type, AnnotatedTypeFactory factory) {
      TypeParameterElement tpelt = (TypeParameterElement) type.getUnderlyingType().asElement();

      if (type.getPrimaryAnnotations().isEmpty()
          && type.getUpperBound().getPrimaryAnnotations().isEmpty()
          && tpelt.getEnclosingElement().getKind() != ElementKind.TYPE_PARAMETER) {
        try {
          ElementAnnotationApplier.applyInternal(type, tpelt, factory);
        } catch (UnexpectedAnnotationLocationException e) {
          // The above is the second call to applyInternal on this type and element, so
          // any errors were already reported by the first call. (See the only use of this
          // class.)
        }
      }
      return super.visitTypeVariable(type, factory);
    }
  }
}
